The violin represents a prime achievement in the evolution of string musical instruments which evolved from more primitive instruments such as the rebec and the lute. The modern day violin can be traced to at least as early as the sixteenth century where many violins were built under the supervision on Andrea Amati at the Cremona school of violin makers in Italy.
In essence, a violin is a set of strings mounted on a wooden box containing an almost closed air space. The wooden box or sounding box consists of a front plate also called the belly and a back plate also called the bottom. Both are arched slightly outward to form broad bell-like shapes. They are joined and supported by ribs or sides. The back plate is carved with chisel, plane and scraper, traditionally from a block of curly maple seasoned for at least ten (10) years and not kiln-dried. In thickness the back plate varies from about five millimeters in the center to almost two and a half millimeters just inside the edges. The sides are pieces of matching curly maple, thinned down to a millimeter all over, bent into shape and glued to spruce or willow blocks set in the corners and at the forward and rear ends of the plates.
The top plate, usually spruce, is split lengthwise from a log and then joined so that the wood of the outside of the tree is in the center of the top, making the grain bilaterally symmetrical. In thickness the top plate ranges from two to three and a half millimeters, and a pair of "f-holes" are cut into each side of the plate. All around the outside of each plate, near the edge, is cut a shallow groove in which is inlaid the "purfling", consisting usually of two strips of black-dyed pearwood and a strip of white poplar.
Attached at the upper portion of the sound box is the neck, which is usually made of curly maple. The fingerboard which lies over a portion of the neck and extends over the upper portion of the top plate is usually made of ebony. The tailpiece at the lower portion of the sounding board is usually made of rosewood or ebony.
The four violin strings, representing the musical notes G, D, A and E are strung so that they stretch over the neck and fingerboard and terminate at the forward edge of the tailpiece. The strings are supported across the center of the violin by the bridge. Traditionally, the bridge has been made of hard maple, such as spotted maple wood.
The combined tension of the four strings of a properly tuned violin comes to around 50 pounds. About 20 pounds is directed straight down through the bridge and against the sounding box. To distribute the load and help the top plate withstand the downward component of string tension, a strip of wood known as the bass bar is glued to the underside of the top plate; running lengthwise and located directly below the "G" string foot of the bridge. The bass bar is usually made of spruce.
To assist in transmitting musical vibrations from the top plate to the back plate, a vertical post is placed inside the sounding box. The post, called the sounding post, is held between the plates by friction and is located 5 to 6 millimeters below the "E" string foot of the bridge.
While violin making is an ancient art, few improvements have been made in the basic violin design since the days of the famous violin maker Antonio Stradivari. One of the most important and neglected elements of the violin has been the bridge.
In general, the bridge stands on the belly of the violin between the "f-holes" and is located so the bottom end of it is lined up with the inner nicks of the "f-holes." The bridge is not fastened to the violin body in any way, being merely kept in its place by the pressure of the four strings. One purpose of the bridge is to keep the strings at a playable height above the fingerboard.
The main purpose of the bridge is to transmit the vibrations of the strings to the belly and back of the violin. The bridge is the principal channel by which the vibrations of the strings pass to the top plate of the violin by way of the bass bar, and to the back plate of the violin by way of the sound post. In consequence of these important functions, the proportions of the bridge and its position on the top plate must be very carefully adjusted to the quality of the violin to which it is affixed. If the bridge is too thick, the vibrations of the strings will not pass with sufficient rapidity to the top plate. The height of the bridge must also be carefully adjusted to the instrument. If the bridge is to high, the tone will be dull and sluggish. If the bridge is too low, a harsh piercing tone will be the result.
The various styles of bridges produce different effects on a violin. The standard commercial style bridge is so stiff that is must be thinned greatly in order to work satisfactorily. If the bridge design is so rigid that it must be thinned greatly, it gains flexibility at the expense of force and strength. As a result, such a bridge does not properly transmit the vibration forces from the strings to the belly and bottom of the violin.
Under tension of the strings, the flexibility of the bridge is such that it amplifies the vibratory excitation of the strings. The bridge height varies from instrument to instrument. The higher the bridge, the greater the downward force on the bridge and the greater the force on the top and back of the bridge. The thinner the bridge, the more flexible it becomes. A significant problem arises with ordinary commercial bridges because they must be made very thin in order to flex at all. By the time the ordinary commercial bridge has been made thin enough for amplification of the string vibrations, the bridge is in serious danger of collapse or warping badly.
Although there have been many designs for violin bridges, most commercial designs are very similar to the design originally created by Antonio Stradivari. In order to work properly, the bridge must be made of spotted maple. The grain of the bridge must be horizontal and its proportions should be just half as thick at the top as at the feet. Such a bridge must be painstakingly made and suffers from the weaknesses described above. Furthermore, a violin bridge of such design and fabrication does not lend itself to easy mass production.